Omnidirectional sign

ABSTRACT

A CYLINDRICALLY SYMMETRIC ILLUMINATED SIGN PRESENTING ITS LEGEND IDENTICALLY IN ALL DIRECTIONS PERPENDICULAR TO ITS AXIS. THE SIGN COMPRISES A THIN LIGHT SOURCE ALONG THE AXIS AND A THIN CYLINDRICAL OUTER SHELL OR REFRACTING CYCLINDER MADE UP OF ANNULAR ELEMENTS EACH COMPRISES MANT REFACTING SURFACES SUBSTATIALLY PARALLEL TO THE CYLINDER AXIS, GROUPED IN IDENTICAL SEQUENCES EQUALLY SPACED AROUND THE INNER PERIPHERY OF THE ANNULAR ELEMENT. EACH SEQUENCE OF ONE OR MORE REFRACTING SURFACES IS SEPARTED FROM ADJACENT SEQUENCES BY SURFACES RADICAL TO THE CYLINDER, AND OTHER SURFACES WHICH ARE OPAQUE TO PREVENT UNWANTED LIGHT FROM PASSING THROUGH THE CYLINDER. THE REFRACTING SURFACES, COOPERATING WITH THE SMOOTH OUTER SURFACE OF THE CYLINDER, THUS PROVIDE PRISMATIC REFACTING ELEMENTS WHICH PERMIT PASSAGE OF LIGHT RAYS FROM THE LIGHT SOURCE THROUGH THE CYCLINDER IN IDENTICAL PATTERNS IN ALL RADIAL DIRECTIONS, INSERTION OF VARIOUS LIGHT FILTERS, MOVING OR STATIONARY, BETWEEN THE LIGHT SOURCE AND THE REFACTING CYLINDER PERMITS CHANGING COLORS OR LENGENDS. DEPARTURES FROM CYLINDRICAL SYMETRY OR FROM IDENTICALITY OF SEQUENCES OF REFRACTING SURFACES ON A GIVEN ANNULAR ELEMENT PERMIT VARIATIONS IN THE LEGEND OR DISPLAYED IMAGE WITH ANGULAR POSITION ABOUT THE SIGN&#39;&#39;S AXIS. THE REFACTING CYCLINDER MAY SUBTEND LESS THAN 360* OR MAY CONSIST OF PART OF A MOVING TAPE OF TRANSPARENT MATERIAL, BENT INTO CYLINDRICAL SHAPE AS IT PASSES AROUND THE LIGHT SOURCE, AND UNPRINTED WITH REFACTING, RADIAL AND OPAQUE SURFACES. IF THE DIAMETERS OF ANNULAR ELEMENTS ARE VARIED, THE SIGN MAY BE GIVEN SPHERICAL, CONICAL, OR OTHER AXIALLY SYMMETRIC SHAPED.

United States Patent [72] Inventor Oliver E. Deal Lancaster, Calif. [21] Appl. No. 724,699 [22] Filed Apr. 29, 1968 [45] Patented June 28, 1971 [54] OMNIDIRECTIONAL SIGN 17 Claims, 44 Drawing Figs.

[51] Int. Cl 609i 13/12 [50] Field of Search 240/106, 106.1;40/130, I32

[56] Reierences Cited UNITED STATES PATENTS 1,682,490 10/1925 Dressler 240/1061 2,344,295 3/1942 Franck 240/1061 2,454,332 11/1948 Mitchell 240/1061 Primary ExaminerRobert W. Michell Assistant Examiner--L. R. Oremland ABSTRACT: A cylindrically symmetric illuminated sign presenting its legend identically in all directions perpendicular to its axis. The sign comprises a thin light source along the aiis and a thin cylindrical outer shell or refracting cylinder made up of annular elements each comprising many refracting surfaces substantially parallel to the cylinder axis, grouped in identical sequences equally spaced around the inner periphery of the annular element. Each sequence of one or more refracting surfaces is separated from adjacent sequences by surfaces radial to the cylinder, and other surfaces which are opaque to prevent unwanted light from passing through the cylinder. The refracting surfaces, cooperating with the smooth outer surface of the cylinder, thus provide prismatic refracting elements which permit passage of light rays from the light source through the cylinder in identical patterns in all radial directions. Insertion of various light filters, moving or stationary, between the light source and the refracting cylinder permits changing colors or legends. Departures from cylindrical symmetry or from identicality of sequences of refracting surfaces on a given annular element permit variations in the legend or displayed image with angular position about the sign 5 axis. The refracting cylinder may subtend less than 360 or may consist of part of a moving tape of transparent material, bent into cylindrical shape as it passes around the light source, and imprinted with refracting, radial and opaque surfaces. If the diameters of annular elements are varied, the sign may be given spherical, conical, or other axially symmetric shaped.

ATENTFU JUN28 197a SHEET 2 BF 4 (9M 5 08mg Fla. /7

OMNIDIRECTIONAL SIGN The present invention relates to illuminated signs, cylindrical in form, in which the legend or image displayed contrasts with the background in degree of illumination.

In particular, this invention contemplates a cylindrically symmetric illuminated sign, displaying any desired legend of letters, numbers, or other symbols arranged along the cylinder axially as shown in the basic example of FIG. 1, or any desired, reasonable pattern of darker and lighter areas, the unique feature of this sign being that its legend is displayed identically in all directions about its axis of symmetry. This means that if an observer were to move about the sign in the plane normal to its axis, the sign would continue to present the same appearance to him, with its legend or displayed image centered along the axis, as shown in FIG. 1. Thus, the sign has no front, back, or sides, but isomnidirectbnal.

For most such signs, the axis of symmetry would be oriented vertically as shown in the elevation view of FIG. I; however, for some individual signs, the axis might be oriented horizontally, with the legend suitably arranged to be viewed omnidirectionally in the vertical plane. Only the vertical orientation of the axis is shown on the accompanying drawings.

For convenience in depiction only, all of the accompanying FIGS. show the legend 1 as black on a lighter background 2; the legend of the actual sign would normally be the lighted portion of the sign, appearing against a darker background, although any reasonable pattern of lighter and darker areas, including that of FIG. 1, for example, is possible using the methods described below.

The sign contains a thin, cylindrical light source 3 along its axis of symmetry. Light passing outward radially from the source impinges upon the refracting cylinder 5, which is made of transparent material, probably plastic but possibly glass, which is annular in cross section, and which bears the legend in the form of properly oriented tiny prismatic refracting elements. For good definition of the legend, the light source must be very bright and its diameter quite small compared to the diameter of the refracting cylinder. Furthermore, for uniformity, the dimensions of the refracting elements should be small compared to the radius of the light source 3.

The refracting cylinder may be comprised, along the axial direction, of a series of individual refracting rings 6; each ring, in turn, consists of a large number of individual refracting elements of one, two, or several types, depending upon the number of lines of the legend or lighted areas of the displayed image which intersect the given ring.

In the following specification, occasional reference will be made to the several sheets of drawings included herewith, as follows:

FIG. 1 shows the basic sign and its minimum essential parts;

FIG. la is an elevation view of the sign. Various sections are taken from this FIG.;

FIG. 2 is a section, in elevation, of the basic sign;

FIG. 3 is a plan view of a single refracting ring which is intersected by a single line of the legend;

FIG. 4 is a detail of FIG. 3, showing the simplest refracting elements;

FIG. 4a is an enlarged view of a refracting surface of FIG. 4;

FIG. 5 is likewise a detail of FIG. 3 with opaque inner surfaces added;

FIG. 6 is a plan view of an individual refracting ring which is intersected by two lines of the legend;

FIG. 7 is a detail of FIG. 6 showing the various inner surfaces in periodic sequence;

FIG. 8 is a tangential section F8 of FIG. 5 of an individual refracting ring showing an angled inner refracting surface 8, to deflect the field of view of the sign downward;

FIG. 9 is an elevation view showing the field of view of the basic sign as compared with the field of view if the individual refracting elements are modified as in FIG. 8;

FIGS. 10 and 10a are tangential sections of individual refracting rings showing the inner refracting surface 8a curved in the vertical plane to broaden the field of view of the basic sign;

FIG. II is an elevation view of the basic sign showing the field of view if the individual refracting elements are modified as shown in FIG. 10 or FIG.

FIG. 12 is a plan view of an individual refracting ring which is intersected by the lighter and darker portions of a relatively complex image;

FIG. 12a is a side view of the ring of FIG. 12, showing the lighter and darker portions of the signs displayed image, as intersected by that ring;

FIG. 13 is a detail of FIG. 12 showing the sequence of inner surfaces of a relatively complex refracting ring;

FIG. 14 is a detail of FIG. 3 showing the periphery of a refracting ring separated into individual outer refracting surfaces;

FIG. 15 is an elevation view of a sign in which the refracting cylinder consists of whole symbols and spacers;

FIG. 16 shows a proposed interlock arrangement between sections and spacers making up the refracting cylinder;

FIG. 17 is a section view F17 from FIG. la, in elevation, showing a transparent inner retaining tube for use when the refracting cylinder consists of separate individual refracting rings or separate whole symbols;

FIG. 18 is similar to FIG. 17 but shows the transparent retaining tube outside of the refracting cylinder;

FIG. 19 shows the basic parts of a machine which might produce the refracting cylinders of a number of identical signs, in a continuous ribbon;

FIGS. 20a, 20b, and 200 show how the ribbon of FIG. 19 might be cut, rolled, and glued to make the refracting cylinders for individual identical signs;

FIG. 21 shows the rolling and inserting of individual symbols into the retaining tube of FIG. 18 for changing the legend of a sign;

FIG. 22 is a section view F22 from FIG. 1a, in elevation, of the sign showing a rotating multicolored light filter around the source;

FIG. 23 is a section view F23 from FIG. 1a, in elevation, of the sign, showing an array of opaque circular baffie plates around the light source for collimation into planes normal to the axis of symmetry;

FIG. 24 is a cutaway view of a sign having a dual legend, with the inner, banded cylindrical filter in its lower position, displaying the first legend;

FIG. 25 shows the same sign with the inner, banded cylindrical filter raised a short distance, so as to display second legend;

FIG. 26 shows a sign in which the color of the legend is changed by adjusting the vertical position of an inner cylindrical filter having alternating color bands;

FIG. 27 shows a similar sign in which either color or legend or both is changed by a rotating inner cylindrical filter with helical stripes and a mixed refracting cylinder with refracting rings offset to form helices;

FIG. 28 shows how either the inner banded cylindrical filter or the refracting cylinder may be cut from a continuous ribbon and joined with an offset to produce the helical patterns required by FIG. 27;

FIG. 29 shows a plan view of an individual refracting ring of a refracting cylinder which is mounted eccentrically and rotated about the center of the light source in order to produce horizontal expansion and contraction of the legend; FIGS. 29a and 29b show the expanded and contracted appearance of the legend;

FIG. 30 shows a plan view of an individual refracting ring in which periodicity of the individual refracting elements is altered to produce a changing image with rotation of the refracting cylinder;

FIGS. 31 and 310 show two possible forms of the individual sequences of refracting surfaces making up the ring of FIG. 30;

FIG. 32 shows a plan view of the sign in which the refracting cylinder consists of a short section of a continuously moving endless tape, to give a moving or changing displayed image; FIG. 32a is a similar sign and moving tape arrangement in which the tape is continuously fed from a reel, past the sign, to a takeup reel; and

FIGS. 33 and 33a show two signs in which the refracting cylinders span sectors less than 360.

The directions of section views or the approximate areas of details are indicated on drawings with the legend F followed by the FIG. number of the section or detail.

FIGS. 8, 9, 10, a, and 11 are concerned with somewhat limited refraction of light in planes containing the axis of symmetry of the sign, said axis being presumed to be vertical. All other FIGS. are concerned with refraction in planes normal to the sign's axis, and all angles discussed regarding these FIGS. are in these planes, which are presumed to be horizontal.

The tiny prismatic refracting elements referred to above lie between tiny plane or curved refracting surfaces, etched or imprinted on the inside of the thin refracting cylinder, and the outer refracting surface of the cylinder.

FIG. 2 shows the arrangement of the light source 3, and the refracting cylinder 5, consisting of the array of refracting rings 6. FIG. 3 is a plan view, section F3 from FIG. 1, of an individual refracting ring 6 which is intersected by a single line of a simple legend 1; the light rays 70 which convey, to various observers, the spot of light indicating the intersection of the legend II with ring 6 in question, are all seen to be bent through the same angle a from the initial radial rays 7, and in the same sense, Thus the spot of light, as seen by each observer, is displaced the same distance D=r sin a where r is the approximate radius of the refracting cylinder, the difference between the inside and outside diameters of the cylinder being small compared to its radius. Each spot of light making up a part of the legend or displayed image is produced omnidirectionally in this same way.

FIG. 4 is a detail F4 of FIG. 3, and shows the simplest arrangement of the inner refracting surfaces 8. The ray of light 7 proceeding radially from the source strikes the individual inner refracting surface 8 at the angle of incidence b and leaves at the angle of refraction b,. The angle of incidence at the outer refracting surface is thus if, as would normally be the case, the outer refracting surface 9 is circular and continuous as indicated in FIG. 4. The angle of refraction a at the outer refracting surface 9 is, in the above case, equal to the total angle through which the radial ray 7 is bent. The refracting surfaces 8 are separated by the radial surfaces 10.

As can be seen from FIG. 4, those rays 7b which strike the simplest refracting surface 8 near its intersection with the radial surface 10 will be bent sufficiently to impinge upon the inside of the radial surface, and will thus be scattered in an undesirable way; it thus becomes necessary to add the opaque surfaces 11 of FIG. 5 to prevent this scattering. The surfaces 11 are normally either to be painted black to absorb the light which impinges on them or are to be silvered to reflect the light back into the source. The minimum width of the opaque surfaces 11 is sufficient to prevent light leaving the inner refracting surface 8 from impinging upon the inside of the radial surface 10. A valuable additional function of the opaque surfaces ll is to take up space on the individual refracting ring 6 and thus permit limitation of the width of the refracting surfaces 8, so that the brightness of the spots of light transmitted thereby may be precisely as desired. In some applications it may be desired for these so-called opaque surfaces to be somewhat translucent in order to offer a slightly lighted background 2.

In the case in which an individual refracting ring is intersected by two of the lines of a simple legend, as with the ring of FIG. 6, the tiny refracting elements must be of two distinct types, one to produce each of the intersections. Thus, each ray emanating from the light source of FIG. 6 is shown split by two tiny adjacent refracting elements into two resultant rays, 70,, and 7a,,, which represent, to the observer Ob. the right intersection, displaced through a distance from the observed center of the sign, and the left-hand intersection, displaced through a distance respectively. FIG. 7 shows a detail F7 of FIG. 6 and illustrates how two closely adjacent radial rays 7 are separated into the individual refracted rays 7a,, and 7a,, by the adjacent refracting elements 8,, and 8 In the periodic sequence S of surfaces 8 8, 10, 11, etc., the total length of the sequence is presumed fixed; the lengths of refracting surfaces 8,, and 8,, are selected to give the desired intensities of the right-hand and left-hand spots of light, respectively, and the opaque surface 11 is simply made long enough to fill out the desired total length. The length of the radial surface 10 is simply sufficient to make the transition from the refracting surface 8,, to the opaque surface 11.

Should a given refracting ring be intersected by the legend in three places, an additional refracting surface 8 is simply added to the sequence, and the opaque surface 11 shortened as required. The same technique is extended to any number of intersections of the legend with a given refracting ring.

The field of view, in elevation, through which the appearance of the legend is satisfactory may be limited for some applications. Techniques for adjusting this field of view are illustrated in FIGS. 8 through II. In order to deflect the region of the best field of view downward, the inner refracting surfaces are given a slight angle 0 relative to the vertical or axial direction 4a in FIG. 8. This angle c becomes the angle of incidence in the vertical plane when the radial light ray 7 impinges upon the inner refracting surface 8. Additional downward refraction occurs at the outer refracting surface 9, which is presumed to be vertical but which may also be placed at an angle relative to the vertical. The alteration downward of the best field of view is shown qualitatively in FIG. 9, in which the field of view 12 of a sign with vertical refracting surfaces is compared with the field of view 13 of a sign having its refracting surfaces inclined relative to the vertical as in FIG. 8. Reversing the angles of inclination 0 permits alteration of the field of view upward, if that is desired.

If it is desired to broaden the field of view of a sign in elevation, this may be done by giving the inner refracting surfaces 8a a curvature, either convex as shown in FIG. 10 or concave as shown in FIG. 10a. In FIG. 11, the broadened field of view 14 is shown for qualitative comparison with FIG. 9.

If, for a given refracting ring, it is assumed that the length of each of the periodically repeating sequences S of inner surfaces is small relative to the diameter of the light source, then the width of each line of the legend which intersects the ring will be approximately that of the light source. The intersection of line and ring will appear to the observer as a row of small rectangular patches of light, each produced by an individual refracting surface. As the number of lines intersected by a ring is increased, the required number of individual inner refracting surfaces per sequence, each with its own value of the angle b, is increased by the same amount, the relative brightness of each line being governed by the relative length of the corresponding refracting surface. If the number of lines is increased until they blend together, broad areas of greater or lesser brightness are produced; the individual inner refracting surfaces can be blended together, as well, producing curved refracting surfaces such as Sun and 800 of FIG. 13. The relative brightness, to any observer, of a given region of the ring will be governed by the radius of curvature of the corresponding regions of the inner refracting surfaces. The outer refracting surface 9 is assumed to be circular.

For example, FIG. 12 depicts the plan view of an individual refracting ring designed to display to any given observer Ob a region of variable brightness l5aa; a nonilluminated region bb; and a region of uniform brightness 1504. For convenience in depiction, relative brightness is indicated by the relative lengths of lines indicating rays of light. A side, or elevation view, of this refracting ring would be as shown in FIG. 12a, which represents a single horizontal band through the total image displayed by a complete sign. In FIG. 12a relative brightness of the image is depicted by relative thickness of the vertical lines, and cylindrical shading is deleted. The distribution of light thus required at each tiny region of the refracting ring in order to display to any observer the regions l5aa, ISbb, and 1500 is illustrated at the lower left of FIG. 12, in which a sector of variable illumination 15; a sector of no illumination 15b,- and a sector of uniform illumination 15c are shown, making up the total sector 15 which can be illuminated from a given point. FIG. 13 is a detail of FIG. 12 showing the required refractingelements. Curvature of the inner refracting surface SM is designed to produce the sector of variable illumination 15a; the point 8bb corresponds to the nonilluminated sector 15b; and the curved inner refracting surface 800 is designed to produce the uniformly illuminated sector 15c. Again, the relative brightness in a given region is indicated by the length of the ray leaving the outer refracting surface 9.

In the preceding discussion, the outer refracting surface of each ring has been cylindrical, bending at this surface having been due to the angle of incidence a,%b, at that surface, established by refraction at the inner surface. If, as in FIG. 14, the outer surface is discontinuous, being broken into small individual surfaces 90, additional refraction can take place at these surfaces. In order to prevent undue scattering, the transition surface 100 must be parallel with the light passing through the refracting ring, that is, at an angle (bb,) to the radial direction. It appears that this would, however, be of value only for signs displaying relatively simple legends, and is assumed not to be done for other cases which follow.

Many applications for signs of this type may require easy assembly of the refracting cylinder and its desired legend from standard parts. The sign of FIG. 15, for example, displays a house number; here each of the individual numbers making up the legend is carried on a separate, shorter, refracting cylinder 16 which can probably be mass-produced quite easily. Opaque spacers 17, between individual symbols 16, may or may not be required, depending upon the design of the symbols. A simple method of interlocking the individual symbols l6 and spacers 17 is proposed in FIG. 16.

Another method for holding the parts of the refracting cylinder together is shown in FIG. 17, in which structural strength is offered by the retaining tube 18. The refracting cylinder 51: may consist of whole symbols and spacers, or may consist of individual rings, held in place by the retaining tube 18, which must, of course, be transparent. Alternatively, as shown in FIG. 18, the retaining tube 19 may be outside the refracting cylinder 5a.

One method whereby a large number of identical refracting cylinders, whether for individual symbols or whole legends,

.might be produced is proposed in FIGS. 19 and 20. The imprinting roller 20 forms the inner surfaces (refracting, radial, or opaque) on the continuously moving ribbon 22 of soft (presumably warm) transparent plastic material, by pressing it against the smooth roller 21. A second, similar, set of rollers paints the opaque surfaces, which stand out from the refracting or radial surfaces. The ribbon 22 is then cut into proper lengths 22a, as in FIG. 20a, rolled as in FIG. 2%, and the cut edges 23 are glued together as in FIG. 20c to form a completed refracting cylinder or part thereof. The imprinting roller 20 may in turn be made in a variety of ways; one possible way is to assemble it from individual toothed discs of a suitable hard material. Each disc would be separately machined so that its teeth would produce a specific refracting ring of each refracting cylinder.

Refracting cylinders produced in this way, if they are of sufficiently flexible material, need not be rolled and glued into a permanently cylindrical shape. Instead, as shown in FIG. 2!, they may be rolled just prior to installation into the retaining tube 19. This arrangement requires that the edges 23 fit closely together so that there is no direct light leakage through a slit; however, it offers a significant advantage for signs whose legend is changed frequently, in that each refracting cylinder can be stored flat when not in use.

Variety may be introduced into the sign s legend by installation of a cylindrical, transparent, multicolored filter 24 between the light source 3 and the refracting cylinder 5, as shown in FIG. 22. The filter may be rotated about the sign's axis to give a continuously changing appearance. Alternatively, the entire sign, including the filter, may be rotated; this arrangement also introduces some. scintillation to individual spots of light making up the legend.

In order to reduce scattering of light in certain signs it may be desirable that all the light rays reaching the refracting cylinder be nearly horizontal. A method of achieving a degree of horizontal collimation is shown in FIG. 23. The array of circular baffle plates 25 must be black in color so that rays leaving the light source at too great an angle in the vertical plane will be absorbed.

Another method for reducing scattering is by plane-polarizing the light before it reaches the refracting cylinder. Thus, if the rotating multicolored filter 24 of FIG. 22 is replaced or augmented by a fixed polarizing filter, that light component most likely to be reflected at inner refracting surfaces having a high angle of incidence b will be removed. An advantage of fered by this is a broadening of the useful width of the sign; without such a polarizing filter, the maximum usable value for angle a is estimated at 30", whereas with polarization at maximum usable value for a should be about 45. This means an increase in the possible width of the legend or displayed image from about 50 percent to about 70 percent of the diameter of the sign.

With signs used for advertising, it may be desirable to present two or more legends alternately. A method for achieving this is illustrated in FIGS. 24 and 25. Here, the refracting cylinder consists of individual refracting rings 28:: designed to present the first legend, the digit 1, alternated with refracting rings 28b designed to present the second legend, the digit 2. The banded cylindrical filter 26, fitted either closely inside or closely outside the refracting cylinder, consists of alternated circular black 27a and transparent 27b bands of the same width as the refracting rings. Thus, in one vertical position of the banded filter 26, the refracting rings carrying the second legend are covered by the black bands, and only the digit 1 is displayed, as in FIG. 24. If the banded filter is raised by the width of one band, refracting rings for the first legend are covered and digit 2 is displayed as in FIG. 25.

A similar method for changing color of a single legend is shown in FIG. 26, in which alternate rings 28a of the refracting cylinder are opaque or translucent and the remaining refracting rings 6 are designed to offer a single legend. Here the banded cylindrical filter 26a consists of bands 270 of color I, alternated with bands 27d of color II. Now, as the banded filter 26a is moved up and down, the color of the displayed legend alternates between colors I and II. If, rather than being opaque, the alternate rings of the refracting cylinder are translucent and perhaps colored, various color changes of the background 2 can be made simultaneously. Use of the vertically moving banded filter as shown in FIGS. 24, 25, and 26 can be extended to more complex combinations of color and legend, as desired; furthermore, the vertical motion can be traded for rotational motion if the bands of the cylindrical filter and the rings of the refracting cylinder are made helical as shown in FIG. 27. Here the cylindrical filter 29 has a black helical band 27aa, a helical band 27cc of color I, and a helical band 27dd of color II. The refracting rings of previous signs are replaced by refracting helices 28m and 28bb, which present the first and second legends, respectively; the helix 28cc is opaque or translucent. Pitch and handedness of the helices on the refracting cylinder Saa are presumed to match those of the cylindrical filter 29. Now, as the cylindrical filter 29 is rotated relative to the refracting cylinder, the displayed legend changes through the following sequence: (1) First legend in color II, as shown; (2) Second legend in color I; and (3) First legend in color I and second legend in color II, superimposed upon one another.

A method for forming a refracting cylinder 5 having refracting helices as in FIG. 27, rather than refracting rings, is shown in FIG. 28. Here, the cut section 220 of a continuously imprinted ribbon as shown in FIGS. 19, a, and 20b, has its cut edges 23 glued together with a vertical offset 30, rather than precisely evenly as in FIG. 20c. The offset 30 must be precisely equal to the pitch of the desired helix, so that the end of a given refracting band for, say, the first legend, must be precisely joined with the other end of an adjacent band of the same legend. In order that the discontinuity in the legend, when viewed from the side having the glued seam 23, is not objectionable, it is presumed that patterns of refracting surfaces for adjacent bands of the same legend are not greatly different; that is, it is assumed that the pitch of the helices involved is small relative to dimensions of various parts of the legend.

A simple method for producing a moving legend is shown in FIG. 29, which offers a plan view of the light source of an omnidirectional sign with the refracting cylinder 5b placed somewhat eccentrically about it. If the refracting cylinder is now rotated about the center 40 of the light source rather than about its own center, the legend, as seen by a fixed observer, will alternately broaden and narrow again, and move from side to side. In addition, some scintillation of individual spots on the legend will be seen by a fixed observer. FIGS. 29a and 29b show elevation views of the sign of FIG. 29, as seen by two observers on opposite sides of the sign. Other types of distortion of the refracting cylinder will produce other types of motion of the legend. Alternatively, the light source may be rotated eccentrically within the refracting cylinder, or may be assymetric. Here, the sign is no longer precisely omnidirectional, since the legend is not displayed identically in all directions; however, it remains omnidirectional in that the legend is still displayed in all directions.

In all the variations of the basic sign discussed in the foregoing, all of the sequences of surfaces (refracting, radial, and opaque) repeated periodically around the inside of a given refracting ring have been identical. Departure from this condition permits design of omnidirectional signs similar to those above except that the legend displayed varies with angular position about the sign; such a sign may be rotated about its axis to display the varying legend to a fixed observer. The observed variation may range from simple motion of the legend or its parts to fairly abrupt changes of the legend, if this is desired. Again, some scintillation of individual spots on the legend will be seen by the observer. If such a sign is to be made, the chief problem is the design and construction of the individual sequences S of surfaces for each refracting ring, as shown in FIGS. 30 and 31.

FIG. 30 is a plan view of a single refracting ring which is part of an omnidirectional sign whose legend varies as a function of the angular position 0, of the observer, about the sign. Assuming that each refracting ring has a total of N sequences S of inner surfaces of equal total length (21rr/N), it is convenient also to consider only N distinct observer directions, spaced Ad =(2n-/N) apart, although the legend is of course observable rma), unaru- IIUHFIHHGD and these rays are (21r/ N)=(360/72)=5 apart. FIG. 31 isa detail of FIG. 30 showing the jth individual sequence S of inner refracting surfaces. The length of the inner surface 8 transmitting ray 7 is rAqb where A I is proportional to I If rA lMHoj is the length of the jth opaque surface, we have that Tv'ififi'itiie lengtli of the opaque surface. If the summafrom intermediate directions as well, due to the width of the light source 3. Assuming also that (1r/6) is the maximum practical angle a of total bending of a ray, each sequence S of surfaces offers more or less illumination through a total angular range 15 of L(1r/6), or (11/3) thus providing a spot of light, of greater or lesser intensity to (N/6)+l observer directions. For the purposes of FIG. 30, it is assumed that N=72, although a significantly larger number would normally be required. In this simple case, consider the legend projected toward the ith observer position 0b,. The individual ring of FIG. 30 produces one thin horizontal band of this legend consisting of 13 spots of light of greater or lesser intensities:

tion of lengths of the refracting surfaces does not permit an adequate opaque surface at the end of the sequence S, the desired legends cannot all be presented at the intensity levels selected. As N becomes larger, the degree of complexity increases and the flat inner surface 8 of the jth sequence may blend into smooth curves as in FIG. 13.

FIG. 31a is likewise a detail of FIG. 30 and shows a possible fonn of the individual sequence S of inner surfaces which might be used as an alternative to that shown in either FIG. 13 or FIG. 31. Here the individual refracting surfaces 8 are separated by opaque surfaces 11. This arrangement permits the various refracting surfaces 8 to be formed by individual dies, each with its characteristic angle 12 and characteristic width Md presumably these dies would be pressed into the material of the refractor while it is somewhat warm and soft. If the required width rA'P is greater than usual, in order to produce an especially bright spot, the same die may be used several times; the total surface 8 may then consist of several surfaces of identical angle b. If this arrangement is used, a specific portion of the width of each sequence S may be reserved for surfaces with a specific angle b. In this case a given refracting surface 8 may extend axially along the refracting cylinder as far as may be required by the legend, and ring structure defined previously may be dispensed with.

A simple extension of the above sign, which presents a changing or moving legend as it is rotated, is shown in FIGS. 32 and 32a. Here, the flexible moving refracting ribbon or tape 50 of transparent plastic bears the legend on refracting bands rather than rings. it becomes a refracting cylinder for an omnidirectional sign only when it assumes cylindrical form as it passes around the light source 3 in the sign proper. The sign is not completely omnidirectional in that it presents an image or legend only in those directions not blocked by the rollers 31; it is estimated that a complete legend can be made observable through a total angle of about 270 about the sign.

FIG. 32 shows a sign in which an endless refracting tape 50 is used. The refracting tape of FIG. 32a is fed from a feed reel 32, is guided by the rollers 31, assumes a cylindrical form as it passes around the light source 3 and displays its changing legend, and is guided back to the takeup reel 33.

The same simple mathematical approach applied to design of the refracting surfaces of FIGS. 30 and 31 can be applied to those of FIGS. 32 and 32a, except that the range of values for 0 and is not limited to 211', and i and j are not limited to N=(21r/ can take any value.

If it is desired to have the basic omnidirectional sign display its legend only in a limited sector of the plane normal to its axis, part of the refracting cylinder may be dispensed with, as shown in FIG. 33. Here the sign fits against a wall and is composed of about two-thirds of the basic sign, although the cylindrically symmetric character is retained; the image or legend is displayed through a total sector of 180. FIG. 33a shows a sign designed to fit at a convex corner, the intersection of two wall; the refracting cylinder covers an arc of about 330 so that the complete legend is readable through a sector of 270.

Clearly any desired arc may be covered by the basic sign. It is anticipated that the moving tape and changing legend signs of FIGS. 32 and 320 would best be mounted at such a corner.

If the diameter is varied from ring to ring, axially symmetric omnidirectional signs other than cylindrical in form may be assembled from, or composed of, individual refracting rings such as those described above and illustrated in FIGS. 3, 4, ea, 5, 6, 7, 8, 10,100,,12, 1211,13, I4, 30, 31, and 31a. The possible general outlines for such signs include spheres and cones, although the outer surfaces must be stepped to retain the desired orientation of the outer refracting surfaces of individual rings. The thin cylindrical light source along the axis of symmetry is presumed to be retained.

Those skilled in associated arts will appreciate the possibility of making various alterations in the OMNIDIRECTIONAL SIGN and various parts thereof, without departing from the principles of the present invention. I therefore desire that such modifications be construed within the scope of the present invention, as defined by the appended claims.

I claim:

I. An omnidirectional sign comprising a refracting cylinder (5) of transparent material and a cylindrical light source (3) along the axis of the cylinder, the diameter of the light source being small compared to the diameter of the cylinder, the cylinder being made up of annular elements each comprising:

a. refracting surfaces (8) which are substantially parallel to the cylinder axis and which are grouped in sequences of one or more, said sequences of refracting surfaces being equally spaced along the inner periphery of the annular element;

b. substantially opaque surfaces (11) of such width as to prevent other light rays except those refracted through the refracting surfaces from being visible through the surface of the cylinder; and

c. radial surfaces (I) which are radial to the cylinder and which join refracting surfaces to adjacent opaque surfaces, said refracting surfaces (8) cooperating with the smooth outer surface (9) of the cylinder to provide prismatic refracting elements which permit passage of light rays from the light source through the cylinder, and cause said rays to form equal angles with respect to the radius of the cylinder, and be repetitively spaced around the cylinder, whereby in each direction radial from the cylinder the refracted light rays will form identical patterns of the light source.

2. An omnidirectional sign as in claim 1 in which the refracting cylinder is divided, along the axial direction, into separately distinguishable refracting rings.

3. An omnidirectional sign as in claim I in which the individual refracting surfaces are not precisely parallel to the axial direction, but instead, are inclined at an angle to the axis or possess a curvature in planes containing the axis, in order to broaden or otherwise alter the normal field of view of the sign in said planes.

4. An omnidirectional sign as in claim 1 in which the individual refracting surfaces may be curved in planes normal to the sign's axis, in order to display an image containing broad lighted areas.

5. An omnidirectional sign as in claim 1 in which the refracting cylinder is divided, along its length, into shorter refracting cylinders each designed to display a separate symbol of the legend, and spacers, said cylinders and spacers being held in place by suitable interlocking edges.

6. An omnidirectional sign as in claim 1 in which the refracting cylinder and its various parts are held in place by a retaining tube of transparent material, located either inside or outside the refracting cylinder.

7. An omnidirectional sign as in claim 6 in which the refracting cylinder representing part or all of the legend is discontinuous at one angular position about its axis and can therefore be removed from the sign, opened from cylindrical to flat, rectangular form, and stored in this condition.

8. An omnidirectional sign as in claim I in which a moving or rotating cylindrical colored filter or other light filter is placed between the light source and the refracting cylinder to produce color or brightness changes in the image or legend.

9. An omnidirectional sign as in claim 1 in which a lightpolarizing filter, cylindrical in form, is added between the light source and the refracting cylinder in order to eliminate that polar component of the light which is most likely to be reflected and scattered at the refracting surfaces, thus permitting a broader legend on a sign of a given diameter.

10. An omnidirectional sign as in claim I. in which an array of opaque circular baffle plates is placed between the light source and the refracting cylinder for collimation of light into planes normal to the sign '5 axis.

11. An omnidirectional sign as in claim 1 in which the refracting cylinder consists of alternated rings of various types including refracting rings presenting one or more legends, and colored, translucent, or opaque rings; and in which a banded cylindrical transparent light filter is placed close to the refracting cylinder, said filter bearing alternated circumferential bands of two or more colors, possibly including black or clear, the spacing and number of types of the bands being identical to those of the rings of the refracting cylinder in order that changes in color, legend, background, or any combination thereof may be effected by relative axial motion between the cylindrical filter and the refracting cylinder.

12. An omnidirectional sign as in claim 1 in which the refracting cylinder consists of two or more helices of various types including refracting helices presenting one or more legends; and colored, translucent, or opaque helices; and in which a helically banded, cylindrical, transparent light filter is placed close to the refracting cylinder, said filter bearing helical bands of two or more colors, possibly including black or clear, the pitch, handedness, and number of helices on the filter matching those of the helices of the refracting cylinder, in order that changes in color, legend, or background or any combination thereof may be effected by relative rotational motion between the cylindrical filter and the refracting cylinder.

13. An omnidirectional sign as in claim 1 in which moderate departures from cylindrical symmetry of either the light source or the refracting cylinder, or eccentric mounting of the light source and refracting cylinder relative to one another, is used to present the legend with somewhat differing appearance in varying directions about the sign, so that rotation of the entire sign will present continuous variations in the legend's appearance to a fixed observer.

14. An omnidirectional sign as in claim 1 in which the refracting surfaces on each annular element of the refracting cylinder are selected to display differing legends or images in the various directions perpendicular to the signs axis, so that rotation of the sign about its axis will offer a changing legend or sequence of legends to a fixed observer.

15. An omnidirectional sign as in claim 1 in which the refracting cylinder consists of a part of a moving refracting tape as it is passed in a circular path, and thus given a cylindrical form, around the light source as its center; the prismatic refracting elements of said tape being selected to display differing legends from the various portions of the tape, so that a changing legend or sequence of legends is presented to a fixed observer.

16. An omnidirectional sign as in claim 1 in which the arc of the refracting cylinder is less than 360 and in which the total sector into which a complete legend or other image is displayed is thus less than 360.

17. An omnidirectional sign comprising an axially symmetric refracting outer shell and a cylindrical light source (3) along the axis of the outer shell, the diameter of the light source being small compared to the diameter of the outer shell, the outer shell being made up wholly or in part of refracting rings of varying diameters each coaxial with the outer shell and each comprising:

jacent rings have different diameters the outer shell will have a stepped appearance, said refracting surfaces (8) cooperating with the smooth outer surface (9) of the ring to provide prismatic refracting elements which permit passage of light rays from the light source through the outer shell, and cause said rays to form equal angles with respect to the radius of the outer shell, and be repetitively spaced around the outer shell, whereby in each direction radial from the sign the refracted rays will form identical patterns of the light source. 

